This invention related to irrigation sprinkler nozzles, and more particularly to a new and improved sprinkler nozzle construction for enhancing the distribution pattern of water from a rotary sprinkler nozzle of the type including a primary or range nozzle and a secondary or spreader nozzle.
In many irrigation applications, particularly in commercial irrigation situations, irrigation sprinklers employ nozzles having two or more outlets, one nozzle, referred to as a "range nozzle" which is designed to produce a relatively large volume stream projected outwardly for maximum distance of throw, and another nozzle outlet referred to as a "spreader nozzle" which is designed to produce a smaller volume stream, and which is intended to fall out close in to the sprinkler for close in watering. In the ideal situation, the combined distribution pattern produced by the range nozzle and spreader nozzle would be a wedge shaped curve with maximum precipitation rate occurring at the sprinkler and decreasing linerally to zero at the maximum range.
While it is relatively straight forward to design a range nozzle to achieve maximum distance of throw, it is much more difficult to design a spreader nozzle to fill in the area between the sprinkler and the donut shaped area of coverage produced by the range nozzle. One reason why it is more difficult to design spreader nozzles to supply close in water is that small sized orifices and passageways have typically been thought necessary so that a relatively small droplet size spray is produced which will fall more quickly to the ground than the larger droplet size stream produced by the range nozzle. This is because smaller droplets have a much larger ratio of surface area to mass than larger droplets, so the small droplets lose energy through aerodynamic friction and slow down quickly allowing them to fall closer to the sprinkler than the larger droplets from the range nozzle. The use of small size orifices and passageways to produce small droplet size sprays have been found to have three major disadvantages. Firstly, small droplets are driven by even a slight breeze away from the intended destination, thereby producing erratic water distribution patterns. Secondly, it is very difficult to flow enough water through the small openings and passageways to produce sufficient water volume to achieve the desired close in precipitation rate, and thirdly, the small size of the openings and passages tend to result in clogs due to entrained particulate matter within the pressurized water system, thereby rendering the spreader nozzle ineffective.
Disclosed in U.S. Pat. No. 5,299,742, issued Apr. 5, 1994 and entitled IRRIGATION SPRINKLER NOZZLE is a rotary sprinkler nozzle construction which includes a spreader nozzle constructed in such a manner to enhance the distribution pattern of close in water without requiring small size orifices and passageways and which produces a spray pattern of controlled size and shape that is substantially unaffected by wind. As disclosed in that patent, the sprinkler nozzle includes a spreader nozzle constructed to produce a generally vertically oriented fan shaped spray with a lower portion of the spray being directed downwardly close in to the sprinkler, and an upper portion of the spray directed upwardly to interact with and become entrained in the stream from the range nozzle. By having a portion of the spray from the spreader nozzle become entrained in the stream from the range nozzle, a portion of the stream energy is transferred to the spray, thereby carrying the spray further away from the nozzle then would otherwise occur, and by directing a lower portion of the spray from the spreader nozzle downwardly, the amount of water applied in the immediate area around the sprinkler is increased. This then results in an overall enhancement of the distribution of water from the sprinkler nozzle without significant loss in overall range.
While use of nozzles constructed in accordance with the disclosure of the aforementioned '742 patent have been found to significantly enhance the distribution pattern produced by rotary sprinkler nozzles and have substantially eliminated the problem of spreader nozzle clogging, one problem that has been found to occur is that due to the relatively high velocity of the fan shaped spray produced by the spreader nozzle, the lower portion of the spray if directed downwardly close in to the sprinkler tends to impact on the adjacent soil with such force that erosion takes place and any seed therein planted is washed away. To eliminate this problem, it has been found necessary to direct the lower portion of the fan shaped spray produced by the spreader nozzle of the '742 patent further away from the sprinkler so that it does not fall to the ground until it has been projected outwardly approximately six to eight feet. This then results in a relatively dry donut shaped area extending outwardly around the sprinkler to approximately six to eight feet. As will become more apparent hereinafter, the present invention provides a new and improved nozzle construction which incorporates a third nozzle outlet in addition to a spreader nozzle of the type disclosed in the aforementioned '742 patent, and which provides close in water from the sprinkler outwardly to about six to eight feet. When the distribution pattern produced by the third nozzle outlet of the present invention is combined with the distribution pattern produced by the range nozzle and spreader nozzle, an overall precipitation distribution pattern is produced which very closely approximates the ideal wedge shaped pattern.